Generally, a dye-sensitized solar cell includes: a transparent electrode including a transparent conductive film formed on a transparent substrate, e.g., a glass plate; a counter electrode including a similar transparent conductive film formed on the surface of a transparent substrate; an iodized electrolyte layer disposed between the electrodes; and a photocatalyst film disposed between the electrodes and on the surface of the transparent electrode. A known photocatalyst film contains a metallic oxide such as titanium oxide (TiO2) and is stained with a photosensitizing dye such as ruthenium.
With this configuration, the transparent electrode and the electrolyte layer are in contact with each other. Thus, a liquid electrolyte may cause leakage of electrons from the transparent electrode to the electrolyte layer, unfortunately leading to a reverse current and lower power generation efficiency.
In order to solve the problem, in a known method for preventing such a reverse current (see Patent Literature 1), a fine film made of semiconductors including titanium oxide and zinc oxide, that is, a so-called buffer layer is formed between a transparent electrode and a photocatalyst film (metallic oxide).